The 2016 presidential campaign _ yes, 2016 _ is in full swing, as Republicans and Democrats slug it out with relentless, unusually early efforts to discredit and demonize potential rivals.

Democrats are after New Jersey Gov. Chris Christie. Republicans are eagerly tarring former Secretary of State Hillary Clinton.

Traditionally, presidential candidates had the luxury of methodically building their own images at this early stage, as rivals did opposition research best used closer to Election Day. Christie and Clinton were doing just that. Christie, inaugurated Tuesday for a second term, planned to build an image of a strong leader able to win in a Democratic state. Clinton is finishing her book on her years at the State Department, with a nationwide tour to follow aimed at defining her tenure on her terms.

Now the rules for running for president are changing. “I don’t know that we’ve ever seen anything like this,” said veteran media consultant Kenn Venit.

Not only can’t the candidates set their own timetables and agendas, but there’s evidence the opposition campaigns may work.

Clinton’s approval numbers, while still healthy, are down. Christie is also slipping since reports surfaced about his administration’s involvement in closing parts of the George Washington Bridge to retaliate against a Democratic mayor who wouldn’t endorse the governor.

A Quinnipiac University poll Tuesday found Clinton up 8 percentage points over Christie in a hypothetical nationwide matchup. Last month, they were neck and neck. A new Pew Research Center survey showed the governor’s unfavorable ratings have doubled in a year.

The results follow two weeks of a nonstop Democratic barrage. The past week alone featured a Saturday night Democratic “rapid response” to the latest Chris Christie news, a reminder that he engages in a “pattern of bullying and political retribution.”

Clinton keeps getting battered, too. When a bipartisan Senate committee last week reported that the September 2012 attacks that killed four Americans in Benghazi, Libya, were “preventable,” Senate Intelligence Committee Republicans went further. Clinton’s actions “made a difference in the lives of four murdered Americans and their families,” they wrote.

The strategy is to plant voter doubts about the candidates’ character and leadership ability, and redefining Christie or Clinton is going to be a difficult, lengthy process. After all, Christie’s tough-guy image and Clinton’s lengthy resume made them popular in the first place.

Already, “Democrats are a little bit behind the curve. Christie has built an image for himself that’s allowed him to weather this bridge scandal,” said Andrew Smith, director of the University of New Hampshire Survey Center.

Similarly, “Clinton has been around a long time, and at this point, you either like her or hate her,” said Iowa Republican Chairman A.J. Spiker.

The efforts to singe them go on and on.

The Christie chronicle began in September, when officials close to him were instrumental in shutting down two of the three bridge lanes linking Fort Lee, N.J., to the George Washington Bridge. Christie apologized, fired aides involved in the incident and said he knew nothing about it.

Since then, the state’s legislators have authorized special committees to investigate. In addition, federal investigators are looking into whether the Christie administration misused federal funds to provide help for victims of 2012’s Superstorm Sandy.

Democrats have pounded away.

“The past couple of weeks have been most Americans’ first introduction to Chris Christie. . . . People are seeing him as America’s bully-in-chief,” said Mo Elleithee, the Democratic National Committee’s communications director.

“Granite Staters are still seeking answers,” said New Hampshire’s Democratic Party.

New Jersey’s Assembly Democrats send email alerts to national political reporters detailing subpoenas issued in the bridge case.

When the media found Christie’s assertion that he had had “no contact” with Port Authority official David Wildstein “in a long, long time” to be untrue, American Bridge 21st Century, a Democratic political group, sent out a minute and a half video reminding everyone of Christie’s stumble.

Those pushing these stories say they’re simply trying to get the facts out.

“The seemingly endless stream of scandals coming out of his administration has definitely taken a toll on his national brand, but each and every one of those wounds is self-inflicted,” said American Bridge spokesman Chris Harris.

New Jersey Assembly Democratic spokesman Tom Hester said he’s sent out material because the national media requested it. Whether all this was tarnishing the Christie brand was “not for us to decide. We are a policy and legislative office doing oversight,” he said.

The Republicans’ battering of Clinton is less relentless, but still vigorous. Since the start of this year, Republican National Committee officials have posted nine items about Clinton on their blog, including two on Tuesday.

The Republicans’ favorite Clinton target is Benghazi.

“At the end of the day, she was responsible for ensuring the safety of all Americans serving in our diplomatic facilities,” said a report last week by Senate Intelligence Committee Republicans, who included possible 2016 presidential candidate Marco Rubio, R-Fla. “Her failure to do so clearly made a difference in the lives of the four murdered Americans and their families.”

The report was another chapter in the Republican narrative. One of the party’s New Year’s resolutions for Obama was: “I resolve to hold myself and Hillary responsible for Benghazi.”

There is some danger of a backlash from all this. Venit warned that the public could sour on candidates and not vote. And if a candidate can dodge the bullets and paint critics as mean-spirited, he or she could emerge stronger than ever.

Still, the parties fear Christie and Clinton, so they feel they have to act sooner rather than later.

Even if they are not engaged in 2016 politics, said Ann Selzer, director of the Iowa Poll, “they’re already national figures. People are paying attention to them.”